1. Field of the Invention
The present invention relates to manufacturing of integrated circuits. In particular, this invention relates to the removal of copper oxides from integrated interconnects by utilizing a high intensity UV light source.
2. Description of the Related Art
Copper thin films are currently being used as interconnection materials in semiconductor manufacturing. As compared to aluminum, a traditionally used material, copper has more advantages which are critical for improving integrated circuit performance. First, copper has a much lower sheet resistivity than aluminum. Thus, for carrying the same amount of current flow, a copper line can be made narrower and thinner than a line made of aluminum. Using copper, then, allows for a higher integration density. Also, narrower and thinner conductive lines decrease the inter-level and inter-line capacitance, which leads to a higher speed and less cross-talk for the circuit. Moreover, copper has a better electromigration resistance than aluminum. Therefore, as metal lines are made thinner and circuitry becomes more densely packed, copper provides higher reliability when used in integrated circuits.
Typically, several interconnect levels are employed in an integrated circuit. Low contact resistance, also known as via resistance, to and between interconnection levels is required.
However, during fabrication processes, a copper surface readily oxidizes even in the air, forming copper oxides, such us Cu2O and CuO. These oxides form a high resistance layer between two interlevel copper lines, which, as known by those skilled in the art, would slow down the circuit significantly.
It is necessary to remove the insulating oxide layer from the copper surface before making a connection with a subsequent copper layer.